[KODAD]

Hello all,
I'm a relatively new member, but have been lurking around sail fora for several months.
I'm on a flexible schedule, but have given myself a roughly 2-3 yr timetable to put into effect my plan of buying a liveaboard blue water cruiser in the 38'-42' range. I realize that ~15-20% of my budget will go towards refitting and provisioning as needed. As I have read the many posts here and at other fora, and books and articles, and as I have been sailing with friends on different makes and models of sailboats, and checking out all of the local marinas, I realised that some of my preferences/priorities have changed throughout the search process. But I have managed to come up with a short list of boats that will fit my needs. To name a couple; Island Packet, Mason, Tartan,Norsemen..ect.
My Question,
Most of the boats I like are 20-30 yrs old, is that too old of a boat? I assume (perhaps incorrectly) that if they're still being sailed, then alot have been refitted somewhere along the way. What are your thoughts, pros and cons, of buying an older boat?
Thanks,
Kodad